The present invention is directed to a device for aligning box blanks in a machine for processing box blanks, for example in a folder-gluer.
A folder-gluer is a machine in which the box blanks are taken one-by-one from underneath a pile and carried through various folding and/or gluing sections by means of belt conveyors in order to finally be gathered flat-folded and glued in a delivery station. These operations may take place in the following chronological order: prebreakage of the first and third blank creases, rearranging the blank the blank so as to have it lie completely flat in the next section, applying a glue, folding the blank along its second and fourth creases, applying pressure to have the glued portion adhere to a portion of the box, and then ejection. At the end of this section, every folded blank is piled in the last section called the delivery station.
In order to obtain an accurate fold along every predetermined crease, it is necessary that the transportation of the box blank through the machine is achieved with neither sidewise nor lengthwise sliding. To this aim, use is made of combined lower and upper belt carriers as well as, in certain cases, a combination of one or several lower belt carriers with an upper ramp or base element which supports pressure rollers.
One of the main problems is the inaccurate blank introduction into the machine. The introduction device usually consists of a lower carrier with multiple belts associated therewith and with a front gauge or gate which coacts with the carrier belt to form a slot which allows only one blank at a time to be passed therethrough. In addition, sidewise positioning jaws, which are adjustable on account of the size of the blanks, are provided.
The sequential feed-in of the blanks can then be achieved by means of elements which act so as to partially and temporarily obstruct the slot extending between the carrier belts and the lower end of the front gauge or gate and, thus, prevent the travelling motion of the lower blank of the pile which is located in the introduction device. The travelling of the blank to be introduced results from the fact that the adherence of its lower surface to the carrier belt is much greater than the friction on its upper surface against the lower surface of the next blank in the pile.
However, when the belts become dirty, they will induce discrepancies in the amount of friction at different locations and, hence, an imbalance of the frictional forces over the width of the belts. This imbalance will cause a skewing of the blank as it is introduced into the machine and causes inaccuracies in the position of the blank in the folding station or section and, therefore, jeopardizes obtaining the folds along the desired creases.
Devices for correcting such an inaccurate alignment are known and are preferably placed in the section which is located just after the introduction device. One of the known alignment correcting devices, also called a rectifier, includes a series of lower and upper rollers arranged in a quincunx on a lower beam and an upper beam which may be separated from one another in order to have the thickness of the travelling blank be taken into account or consideration. The rollers of the upper and lower beams are driven by means of a unique flat belt which will transmit its travelling motion through the medium of pulleys fitted on the axle of every roller. The device which will allow the separating of one beam from the other will include, among other things, a device which insures a permanent and variable pressure application of the upper rollers on the blank upper surface. Furthermore, the upper and lower beams are arranged in a definite and invariable angle with regard to the lengthwise axis of the machine.
The device includes, moreover, a lengthwise guiding rail. Because of the angle of the upper and lower beams, the rollers act on one of the sides of the travelling blank and cause the application or movement of its edge against the lengthwise guiding rail. This true alignment has the effect of placing the blank in a desired position so that the creases will be perfectly parallel to the lengthwise axis of the machine.
However, the funnel-type effect thus created may, in certain cases, apply too much pressure on the blank to force it against the lengthwise guiding rail and cause damage to the edge of the blank. Moreover, it is necessary to manually adjust the room left at the entrance of the rectifier between the blank edge and the lengthwise guiding rail. This adjustment is variable on account of the blanks quality and cannot be easily automated. Another drawback remains in the fact that the action of the upper rollers on the blank takes place between the lower rollers and not on their vertical axes and, thus, this action tends to corrugate or bend the blank which will impair the blank's true alignment in case of excessive pressure application. Finally, this type of rectifier has to be removed from the machine if its use is not acceptable for the box blanks being processed. The dismantling and transforming of the rectifier from the folder-gluer section will consume considerable time and, thus, cause the machine to be out of service.
U.S. Pat. No. 5,019,026, whose disclosure is incorporated herein by reference thereto and which claims priority from the same Swiss Application that resulted in Swiss Patent 678 707, describes another device for aligning box blanks. This device includes a movable lengthwise guiding rail, a lower endless belt which is driven and supported by rollers and a row of upper rollers, each of which is fitted on the end of a lever which pivots around a horizontal axis. The lever itself is attached to a support which will pivot around a vertical axis. The ends of every horizontal lever axle is equipped with a flexible element which is attached to a corner member that can be moved horizontally relative to a fixed lengthwise beam secured to the frame of the machine so that each of the supports for the levers of the rollers can be pivoted to change the angle of attack of the rollers relative to the guiding rail. The pressure adjustments of the upper rollers is achieved by means of a primary spring located between the pivoting lever and a guide rod which is fixed on a ramp or base element which, in turn, is fitted on the fixed lengthwise beam owing to secondary springs which surround a threaded adjustment rod screwed on the lengthwise beam.
Functioning almost properly, this device, however, is expensive to construct, since it relies on each roller associated to its lever to be provided with an individual pivot support, a flexible element completing each pivoting in the vertical direction as well as a special corner piece which is horizontally movable in order to force the simultaneous pivoting of all of the levers.